Fats, oils, and grease (FOG) are present in meat fat, food scrap, cooking oil, shortening, lard, gravy, butter and margarine, and food products such as mayonnaise, salad dressings, and sour cream.
FOG poured down kitchen drains (commercial and residential) accumulates inside sewer pipes. As FOG builds up, it restricts the flow in the pipe and can cause untreated wastewater to back up into homes and businesses, resulting in high costs for cleanup and restoration. FOG discharged into septic systems and drain fields can cause malfunctions, resulting in more frequent tank pump-outs and other expenses.
Restaurants, cafeterias, and fast-food establishments can spend tens of thousands of dollars on plumbing emergencies each year to deal with grease blockages and pump out grease traps and interceptors. Some cities also charge businesses for the repair of sewer pipes and spill cleanup if they can attribute the blockage to a particular business. Some cities also add a surcharge to wastewater bills if a business exceeds a specified discharge limit. These expenses can be significant.
Communities spend billions of dollars every year unplugging or replacing grease-blocked pipes, repairing pump stations, and cleaning up costly and illegal wastewater spills. Manholes can overflow into parks, yards, streets, and storm drains, allowing FOG to contaminate local waters, including drinking water. Exposure to untreated wastewater is a public-health hazard.
Communities, counties, and water districts are grappling with the issue of how best to handle grease trap wastes. Most wastewater treatment plant managers feel that from a technical point of view, it is best to have regulations requiring restaurants to have grease traps pumped regularly, and to have the waste discharged at wastewater treatment plants where it can be properly treated and disposed of. However, local realities often create far less effective solutions to this problem. In some areas, there are no legal or permitted approaches to disposing of grease trap waste, forcing it to be done illegally. Data collection in such areas is essentially impossible. Many cities and municipalities lack an adequate grease management program, and few have implemented basic operations to adequately handle grease trap waste. Under these circumstances, reaching satisfactory and conclusive goals becomes difficult at best. Many cannot keep up with the growing inflows of grease trap refuse generated by their expanding communities and lack adequate budgets for necessary expansion.
Meanwhile, the Environmental Protection Agency (EPA) continues to tighten its requirements for disposal of grease trap refuse, exacerbating resources to meet existing regulations for disposal of these materials. The problem is so severe in some areas that many cities do not enforce grease trap waste collection for lack of alternatives to process this waste in accordance with EPA requirements. The problem intensifies as the EPA imposes further restrictions on existing sites, and potential alternative locations continue to compete with new urban developments. Lack of effective treatment of grease trap waste results in higher costs for treatment of wastewater for municipalities and higher costs to the customers for servicing grease traps.
Cities, municipalities, and water districts handle grease trap waste in different ways. In some areas, where land is available, grease trap waste is delivered to a soil regeneration operation where oily waste and greases are bioremediated using microbes and nutrients. Materials are blended and composted, and the product is used as topsoil for the final cover on closed landfill sites. Other municipalities rely on septic tank service companies or grease trap services to treat their own grease trap waste collections. Waste sludge (FOG and other materials) is separated or decanted from water; the pH of the sludge is adjusted with lime; and then the material is land spread, in accordance with permits from county and state environmental agencies. Most of these companies essentially do a material pick-up and land filling of solids after water is removed.
In some cities, pump trucks drive to designated sites and discharge grease trap waste to manholes that provide a direct path to the wastewater treatment plant. In effect, restaurant grease is prevented from flowing through the narrow drains and piping at the beginning of the collection system, but is re-injected into the main sewage stream near the treatment plant where the lines are wide and plugging is not a concern. More commonly, trucks are required to discharge grease trap wastes at the wastewater treatment plant where accurate records can be kept and sources can be monitored.
Other solutions also exist. Among them are grease trap pumping companies that dewater the waste and haul the grease cake to refuse incinerators. Others use a bioremediation process (bacteria) to convert grease to inert solids. Gray water enters the treatment plant and solids are conveyed to the landfill.
Biological remediation for grease trap waste treatment also includes aerobic and anaerobic treatments. The aerobic treatments are represented by the use of lagoon systems, bio-filtration, and activated sludge processes. The anaerobic processes are based on different bacterial treatments to decompose organic solids and liquid waste, and other materials, into soil augmentation substances, biological fertilizer, or biogas.
U.S. Pat. No. 5,458,780 for Method of Treating Waste Water, issued to Evans, discloses a waste stream mixed with a solvent that absorbs the oily material without dissolving in the water phase. The remaining water/solids mixture is then separated by vibratory screening, and the solids are again contacted with solvent to remove the bulk of the remaining oily material. The remaining mostly solid material is screened again and then dried to remove any remaining solvent. The solvent is processed to remove the dissolved oily material, which is then sold or discarded. The water from the screening and drying steps is processed to remove any solvent entrained with the water, and the resulting solvent, solids and oil-free water is discharged.
U.S. Pat. No. 5,543,050, for Grease Trap Wastewater Treatment Process, issued to Roshanravan and assigned to Mel Darling-Delaware Company, Inc., discloses a system that uses both aerobic and anaerobic treatment processes on grease-trap waste contents. The system initially screens the wastewater to remove larger solid-waste matter particles. The wastewater is next anaerobically and aerobically processed. The anaerobic and aerobic processes use dissolved air flotation clarifiers utilizing gas entrained water to remove solid-waste matter from the wastewater. The anaerobic and aerobic processes also use digester apparatus which break down the solid-waste matter of the wastewater. The anaerobic digester uses anaerobic biological processes for breaking down the solid-waste matter while the aerobic digester uses aerobic biological processes. The two by-products of this system, the clarified wastewater and the composted solid-waste matter, are both more ecologically acceptable alternatives than dumping the grease trap contents into a landfill site.
U.S. Pat. No. 6,015,496, for In-Sewer Treatment of Wastewater and Sludges, issued to Boris M. Khudenko, describes a method and apparatus for in-sewer wastewater treatment comprising steps of largely spontaneously growing acidogenic bacteria in sewer lines and providing methanogenic bacteria in those lines. Methanogenic bacteria can be grown using wastewater, solid, or other waste, or other organic feedstock as a substrate. Methanogenic bacteria can be cultivated at a wastewater treatment plant or at other locations in special reactors, or provided from anaerobic wastewater pretreatment plants. Digestion gases can be either vented out or collected and used.
U.S. Pat. No. 7,070,693, for a Process for Treating Septage, issued to Robert J. Kelly, discloses a process and apparatus for the treatment septage, or grease trap waste. The process converts the septage into biosolids (sludge) and water dischargeable into the environment. The treated septage achieves pathogen reduction and reduced vector attraction. Treatment of septage by pasteurization causes the destruction of harmful pathogens. Pasteurization of septage having high water content provides for even temperature elevation and distribution of heat within the thermal mass of the septage allowing for consistent pathogen destruction. An alkaline compound is utilized to form a filter cake from the solids fraction of the pasteurized septage preventing vector attraction, while producing a beneficial biosolid. The liquid fraction of the septage is treated by biological process allowing for its discharge into the environment.
Some grease trap pumping services process their collections and separate some of the grease found in the refuse by “skimming” the grease that surfaces in the water, pumped along when servicing the grease traps, after it settles in holding tanks or dewatering facilities. The reclaimed grease may be put to many alternative uses, such as animal feeds, etc.
For example, U.S. Pat. No. 5,601,715, for Multi-Stage Grease Trap Filter and Skimmer, assigned to New Pig Corporation by Dennis G. Middleton and Robert J. Starr, discloses an apparatus for removing grease from a compartmental grease trap that has water provided therewithin so that grease forms a layer atop the water in the trap. A filter media then skims off the layer of grease (claim 17).
United States Patent Application No. 20050085653, by Juan Miguel Garro, et al., for a Method for Fabricating Grease Trap Waste and Uses of Dractions Therefrom, discloses a process for producing unsaturated and saturated free fatty acid from trap oils, trap greases, brown greases and grease trap waste as starting material. The process consist in subjecting the starting material to a pretreatment, a first purification step, a fractional step, a second purification step and eventually a hydrogenation step. Methyl esters of unsaturated and saturated free fatty acids, oleic acid and stearin is obtained from this process.
Although each of these processes renders somewhat of a solution, at least partially, a common shortcoming for all is the fact that most of the fats, oils, and grease found in the grease trap goes to landfills or is biodegraded without further benefits or tangible results.
Bioremediation in any of its forms (aerobic or anaerobic) is a slow process. It requires significant equipment investment and demands open areas for proper handling of the aerobic processes. Biogas production would be, perhaps, one of the few by-products that can offset some of the costs associated with the actual process of grease trap waste treatment. All bioremediation alternatives require controlled conditions for proper development and results.
Controlled processes are often expensive and hard to replicate. Furthermore, bioremediation activity tends to be very dependent on climatic and ambient conditions.
Burning dewatered grease cake may facilitate EPA compliance when disposing of these residues, but adds no value to the process and, in fact, increases the costs of grease trap waste treatment associated with the handling, transportation, and burning of these solids from the dewatered grease trap refuse. This alternative is not available to most cities and municipalities because many lack incinerator facilities.
Discharging grease trap refuse at the entrance of wastewater treatment facilities may facilitate avoiding clogging due to the water flow and pipes' diameters, but it certainly affects the operational costs of the wastewater treatment facility as a result of having more solids and organics to be dealt with at this stage. With this method, no benefits are obtained from the grease trap waste.
Several brands and types of biological grease digesters could be added to grease traps to reduce the amount of grease that accumulates in it. Many of these are hybrid bacteria designed to convert the grease to less problematic waste like carbon dioxide and water. Many advertise reduction of noxious odors. However, some drain cleaners and bacterial agents may only soften the grease and transfer the problem further downstream, even when used properly.
While some of these solutions may serve the purpose of dealing with the disposal of grease trap waste, none of them provides an easy to implement, simple alternative for effectively handling grease trap waste and recuperating (recycle) FOG material found in it.
It is therefore an object of the invention to process grease trap waste or refuse to remove all organic matter to facilitate its disposal in accordance with the Environmental Protection Agency (EPA) established standards, and reclaim all fats, oils, and grease found in it.
It is another object of the invention to remove all fats, oils, and grease found in grease trap dewatered sludge by employing a dissolving procedure. The procedure is based on either organic or inorganic solvents (hydrocarbons or organic products with lipid-dissolving properties), which can be flammable or non-flammable.
It is another object of the invention to separate and remove all organic matter found in the grease trap waste to facilitate its disposal in accordance with EPA regulations.
It is another object of the invention to process grease trap dewatered refuse encompassing the physical separation of the dissolved fats, oils, and grease, and other compounds in the solvent from the inert solids.
It is another object of the invention to process grease trap dewatered refuse to obtain, after the separation stage, a solid that is free from organic materials that can be disposed of in accordance with EPA guidelines and regulations.
It is another object of the invention to process grease trap dewatered refuse and recuperate the solvent used at the separation stage, delivering the recycled solvent back to a pre-mixing tank for its continued use.
It is another object of the invention to process grease trap refuse and separate all fats, oils, and grease found in it, to obtain a homogenous grease or oil, free from inert materials, water and solids, suitable for other oleo-chemical processes and applications.